Manufacture of electric circuit components



Feb. 26, 1952 P. EISLER' MANUFACTURE OF ELECTRIC CIRCUIT COMPONENTS 7 Sheets-Sheet 1 Original Filed Feb. 5, 1944 R5 C Cg 0 F/GZ (9 uAer/ial Feb. 26, 1952 EISLER 2,587,568

MANUFACTURE OF ELECTRIC CIRCUIT COMPONENTS Original Filed Feb. 3, 1944 7 Sheets-Sheet 2 P. EISLER MANUFACTURE OF ELECTRIC CIRCUIT COMPONENTS Feb. 26, 1952 7 Sheets-Sheet 3 Original Filed Feb. 3, 1944 Feb. 26, 1952 P. EISLER 2,587,568

MANUFACTURE OF ELECTRIC CIRCUIT COMPONENTS Original Filed Feb. 5, 1944 7 Sheets-Sheet 4 F/GS Feb. 26, 1952 P. EISLER 2,587,568

MANUFACTURE OF ELECTRIC CIRCUIT COMPONENTS Original Filed Feb. 3, 1944 7 Sheets- Sheet 5 F/GS."

Inventor w Attorney Feb. 26, 1952 P. EISLER OF ELECTRIC CIRCUIT COMPONENTS MANUFACTURE '7 Sheets-Sheet 6 Original Filed Feb. 5, 1944 Inventor Feb. 26, 1952 E L 2,587,568

MANUFACTURE OF ELECTRIC CIRCUIT COMPONENTS Original Filed Feb. 3. 1944 7 Sheets-Sheet 7 Inventor Patented Feb. 26, 1952 MANUFACTURE OF ELECTRIC CIRCUIT COMPONENTS Paul Eisler, London, England, assignor to Hermoplast Limited, London,

of Great Britain England, a corporation Original application February 3, 1944, Serial No. 520,991. Divided and this application February 27, 1948, Serial No. 11,798. In Great Britain February 2, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires February 2, 1963 8 claims. (01. 41-43) This invention relates to the manufacture of electrical apparatus, and particularly to the production of electric circuits and parts thereof.

A principal purpose of the invention is to facilitate and cheapen quantity production of electric circuit components, such as the resistances, inductances, transformers, tubes, and in terconnecting networks or circuit connections of radio apparatus, the windings of iron-cored transformers and dynamo electric machines, the connecting networks of switchboards, the conductors of heating appliances, and generally of any electrical circuit component which it may be convenient to manufactureby the methods herein disclosed.

A further purpose of the invention is to facilitate the production of electrical circuit components, even though they be not needed in great quantities, in which a high degree of precision is required in the dimensioning or relative location of conductors'such as cannot readily be obtained by known means.

Yet another object of the invention is the production of surface heating elements in which the conductor also constitutes or carries an ornamentation.

Other objects of the invention will appear from the description following.

Most electrical components essentially comprise metal parts conducting electric current sup- 2' ported upon an insulating base, or with interposed insulation upon a metal base.

The invention consists in the production of the metal electric conductors in position upon their insulating support by a process based on the printing of a representation or pattern of the conductive metal.

The common way of building up an electrical circuit or circuit element is first to draw metal into wire, that is to say make a linear conductor, and afterwards to shape this conductor into coils and networks. By the application of the methods of the printing art the invention brings the metal conductor of the circuit component into existence in its final form, or in a develop- 1 ment of that form upon a plane or cylindrical surface. r

A typical instance of the invention comprises the steps ofpreparing by any of the well-known methods ofthe printing art, a printing plate a ferentiating on that surface the areas which are required to be conductive from the areas which description of the production of various circuit components by its aid. This description to the accompanying drawings in which Figure 1 is a diagram of connections of a radio receiver.

Figure 2 is a diagram showing the approximate lay-out of the components of this receiver.

Figures 3 and 4 show two part schemes of connections prepared for the purpose of applying the invention to the manufacture of the circuit connections of this receiver. 7

Figure 5 is a cross-section illustrating the making of connections between one part scheme of connections and another and between the circuit leads and a component by means of an eyelet.

Figure 6 is a cross-section illustrating the making of connections between one part scheme of connections, and another and between the circuit leads and a component by means of stitching Wire.

Figure 7 is a pattern of fiat spirals illustrating the making of inductance'coils according to the invention by printing with the additional step of folding.

Figure Sillustrates another way of joining parts of a component.

Figure 9 illustrates a printed pattern of parallel conductors having many useful applications.

Figure 10 is a pattern of lines on a principal sheet and a connector label illustrating the making of a helical inductance coil according to the invention by printing with the additional steps of winding the principal sheet and attaching a connector label. a.

Figure 11 is a section of a helical inductance refers and its label showing'how the label is positioned by embossing.-

tern of parallel lines.

Figures 13 and 14 illustrate themakingof an inductance from a patternor rectangles withthe The diagram of connections or ihook-iup' shown' in Figure 1 forms no part of the invention,: is'

substantially known, and therefore will not be described further than is necessary to' assist the understanding of the later figures. It is seen to consist of valves V1, V2 etc., resistances P1, R1, R2 etc., inductances such as L', capacitances-ci, C2,

etc., an output transformerLS,and a network of conductors by which these othencomponents are connected together. It is the production'of the connecting network that will first bestudied. The radio engineer charged with theamanufacture of a radio receiver according to Figure 1, must first plan the lay out of the several com ponents, including the connecting network, and produce a lay-out :and wiring .plan such iasiis sh'ownin Figure '2. The design ofrtliisJay-nut is again a matter for:theradioengineer-with which the present inventionis'not primarily concerned;

though the radio engineer familiar with the present invention will naturally in planning his.:layout have regard to the fact that such "andsuch components of it-are to bemade by the rnethods of"-the present'invention. The correspondence between Figures 1 and 2 is sufficiently "apparent from the references upon the severalrparts already mentioned. I It will be noted that the circuit connectio shown in Figure 2 involveseveral instances of crossing conductors; for instance the connection from-LS to V3 crosses the connection "from Rate V3. Inwiring with pre-tformed:wires'rsuch Klonnecti'onsw'are kept separate by suitable disposition in three dimensions; Figure 2 is not intended to represent such disposition; indeed some roomductor-s are displaced to one side merely for the sake of clearness.

sired relation and connected together :where necessary. 7 I

In the present instance the whole of the-circuit connections can conveniently be set out in "two planes-and they are shown'soset outlinFigures B and 4. The general resemblance ofFiguresfS and 4 to the lay-out plan of Figure 2 can beiseen at a glance, and the location of various com: ponents other than the network itself can'readily berecogn'ised. For example, V1, V2, Vaand V4 in Figures 3 and '4 markthe location in the network of thetubes or valves indicated by those referen'ces in Figures 1 and'2. Itwill'be seen'that if Figure 4 be-directly superposed on Figure? the 1 valves, or rather-valve holders, indicated -in the latter-ffigure come in "the places to which valve connections converge in Figure 4. Figures will similarly register with Figure '2 and with Figure 4 if turned {me downward. If the correspondence of these figures'be studied in detail it'willbeseen that some conductors shown in Figure 2 "appear in part in Figure 3 and in par-tin Figure 4;rcr example the connection'betweenvz, C9 andRw in Figure '2 is represented by "the connection afb from the position of V2 in Figures, the connectionfb, 1c in.Fi gure 3, and the connection 0, d in Figure 4. Provision has to'be madefor joining these connections into one conductor in the finished articles; for this reason the parts of it are drawn :so that their ends overlap when Figures 3 and 4 are superposed back to back; thus the points b and c of Figure 4 overlap and register with the points b and c of Figure 3.

Tomake possible the employment of universal tools,' as hereinafter described, in the manufacture o'f'various schemes of connections, of which Figures 1 and 2 are only one example, it is convenient: to limit the possible positions of junction points 'such "as b and c. For this reason .it-is of advantage to prepare the drawings of the lines of .the grid arein'dicatediby the lines 2| passing through "the .point e inboth 3mm 4. V 7

From, the drawings, Figures 3 and ::4,-:printmg plates are prepared by any oi'th'e usual .methods of the printing .art. Theseprinting :plates may, "forxexample, Joe engravings .on :metal, .or lithographic -stones',for .theyimay be prepared by any usual photomechanical:process, or they may be photographic plates. The printing plates'so produced .may be in relief, in "intaglio, :or pianographic, according to the .methcdof production. Fromithe two printing platesso produced any desired number of identical prints of the'circu'it component maybemade. In one form of 'thecinvention, convenient for the instance 'under consideration, j the :prints are made" upon a composite material consisting of metal foil upon. an insulating tm'cl -:ing.{v The thicknessand nature of the 'foil and 'of the backin depend upon the particularnprocess chosen for :converting the imprint :of' the circuit :com-, ponentinto a circuit component; Metallised or metal-coated .paper is one :material; .it-:is pref erable to impregnate the paper with anacidresisting varnish made'of a suitable plastic. 0r metal foil may be coated'with varnishv or with a layer of plastic of "the desired thickness. -'Or a metal coating maybe applied to apreeformed sheet of insulating materiaLsuch as a plastic. Zinc, aluminium, and copper may be married among suitable metals.

For the purpose of the particular example of the invention now under consideration the print is 'made with an 'a'cidresistant inkupo'n the metal side of such compositematerial. Except where'the'pattern to be printed is very fine it is' an advantage to imparta grain to themetal surface by use of an etching bath, or by abra sion or otherwise, prior to printing. "Thefprint may be made directlyfrom the printing" plate or by the off-set method. -"Io ensure a print freefrompinholes, the print may be overprinted, or otherwise reinforced; The print is naturally identical with Figures 3 and '4, and those Figures equally represent the drawing fromwhich the printing plate was prepared, and the print madefrom the plate upon the metal surface'of acomposite sheet. t

The part circuit icomponents'are next per forated at an the points at which junction has to be madebetween the conductorsof-the sheet corresponding with Figure 3 and'those on the sheet corresponding 'with Figure-4, that is "-to say at all points such as cl The restricted locationof such junction points as above described.

enables all the perforations, whether for these particular components or for any other circuit they may be punched out prior to etching, for

instance simultaneously with the perforation, so

as to even up the extent of etching necessary all over the print.

The sheet is then etched in the well-known manner of the printing art, in a bath suited to the particular metal employed, but with this difference from the usual etching of a printing process that the metal not protected by the resistant ink is wholly etched away. To permit of this complete etching away without undue undercutting of the protected parts it may be convenient, as is commonly done in preparing printing plates, to interrupt the etching and re: coat the surface, for instance with a fatty ground, which can be made to protect the sides of the etched lines as well as the outer surface. When etching is complete the ink may be washed ofi.

It will be clear that Figures 3 and 4 equally represent the etched print, that is to say they may be regarded as depicting a sheet of insulating material coated with metal over the shaded parts only.

The two part circuit components are now superposed back to back and metallic junctions are made between them at all the perforations. Such connections may be made in the manner now common in the radio art by means of eyelets. Figure 5, for example, shows a cross-section of a small portion of an insulating sheet 22, having conductors 23 on each side of it produced byprinting methods such as that above described or those described hereinafter, and

the conductors on one side are joined to conductors on the other side, and to the terminal tags of other circuit components such as the resistance 24, by eyelets or hollow rivets 25. .01 'such connections may be made by wire stitching, in wire staples, or wires bent twice at right angles .into 8 form as seen at 26 in Figure 6, and the terminal wires 2'! of a component such as the fixed capacitance 28 of Figure 6 may be used for such stitching. The eyelets or wires are preferably tinned and solder-painted, so that the joints may subsequently be perfected by soldering. This operation also may be performed by a heated universal tool in which soldering bits are set at the position of the junctions of the circuit component in course of manufacture. If desired the metal may be pro tected and insulated by a coating of varnish except over points required to be accessible for purposes of testing or the making of further connections.

The circuit may be tested by a universal testing appliance which permits of contacts being set in desired positions on a surface.

If desired a single printing plate may reproduce the two representations, Figures 3 and 4., side by side, on the same composite sheet. In that case the conductors developed from the print are superposed by folding the sheet back upon itself with the conductors outward.

-- It will be seen that the essence of the particular method of producing circuit components just described is the preparation of a printing plate, the printing from it of a representation of the conductors of the circuit component,

thereby diilerentiating on the printing surface the areas which are required to be conductive from those which are required to be non-conductive, and the subjecting of the surface to an after treatment which operates difierently on the differentiated parts and converts the differentiation into a differentiation of conductive and non-conductive areas. The imprint made is a positive imprint, that is to say the inked part represents the conductors of the component; and the imprint is made on metal; and

the component is completed by removal of metal from the unprinted areas.

In the particular method just described removal of metal was effected by chemical etching; it could equally well be removed by electrolysis, the printed surface being made the anode in a bath of electrolyte which attacks the foil. In the case of some metal fails, for example aluminium, it may be convenient, instead of removing them wholly, to convert them into non-conductors, a process well-known as anodising, and which also consists essentially in making the metal an anode in a suitable electrolytic bath.

Instead of producing the circuit component from the imprint by removal of metal it may be produced by adding metal. For example, the printing plate may be prepared to print a nega-- tive of the circuit component, that is to say to cover with ink those parts of the surface which are to be non-conductive. A negative imprint can be made in insulating ink upon metal foil say zinc foil, on a suitable backing, and additional metal of a different kind, say copper, can be added to the parts not inked by electro-deposition, the printed foil being made the cathode in an electrolytic bath. Or the printed foil may be subjected to a galvanising process by coating it with flux and passing it through a bath of molten metal, which must naturally be a metal of low melting point such as Rose metal or a soldering alloy, melting at a temperature which will not harm the insulating backing. The metal foil must subsequently be removed, at least over those areas covered by the ink and therefore not'covered by added metal, and this may readily be done in an acid bath which attacks the metal of the foil but not the added metal.

The printing plate may be a photographic plate or film, in which case the imprint is made by contact printing or projection upon a sensitized surface. For example a metal plate may be gelatine coated as in zincography, and printed from a negative of the circuit component. The coating is hardened where it is exposed to light and elsewhere may be washed away, and the metal so uncovered can be etched away, preferably in stages. Or the hardened gelatine may be inked and dusted.

These various methods by which an imprint of a circuit component is converted into a circuit 7 component are to be regarded as illustrative examples only; to those acquainted with the printing art, from which most of the individual steps employed are taken, with some modification, it will be obvious that many other modified operations 'or modified sequences of operations may be adopted according to the nature of the circuit component that is to be made. A few of these are mentioned below in connection with the making of particular. circuit. components.

Reverting to the radio receiverof Figures '1 and 2, there has so far been described the pro-.

duction of. only one of its circuit components, namely the circuit connections, which can be produced by any ofthe methods above described. To what extent it is convenient to employ the invention in the making of other components of therradio receiver is a question to be answered on economic grounds. The illustrative examples next described show that other components may readily be made by similar methods, and those examples will assist'in indicating how the design of components may usefully be modified with a view to their being manufactured by a printing process.

The inductance L'of the antenna circuit may take the well-known if less usual form of a flat spiral, suchas one of the spirals 3| of Figure '7. On accountof exigencies of drawing the spiral isshown as consisting of a few Well spaced turns; the printing methods above described, particularly, for example, the method of printing and etching first above described, permits of the making of a spiral of hundreds of turns spaced apart no more than a few thousandths of an inch. Hence a single spiral'will commonly suffice for the inductance L. The spiral is drawn outv carefully, a printing plate is made from the drawing-an imprint is made on-metal foil, on aninsulating backing, and the metal not protecte'd is-etched away; or another of the procedures, above .described is followed.

If greater inductance isrequired than can .conveniently' be obtained in a single spiral, for example if a winding of a great number of turns is required with or without an iron core, the spiral pattern may be repeated asoften as desired. A convenient pattern is that shown in Figure 'I, which consists of pairs of spirals 3|, 32, joined at their outer ends. The free ends of the spirals form junction points 34, and it will be noted that some of these, but not all, have the same angular position as each other; for example no. two of the spirals in the second row have their free ends in the same position, but each of them has its free end in the same position as has the spiral beneath it in the third row. This pattern may be printed on metal on an impregnated paper backing which can readily be folded. After the print has been'metallised in one of the ways above described and its surface coated (or left coated) with insulation, except at the junction points, the sheet is folded about the line 3535. The junction points become superposed in register and may be connected by spot-welding by a universal-welding tool-analogous to the soldering toolabove mentioned. Or they may be joined as explained with reference to Figures 5 and 6. After the junctions have been made the print is further folded. about the lines 3636, the lines 31 and thelines 3838. By a small modification inthe pattern, junction points may be made. to abut upon one another on folding, as shown "in Figure '8,which is a cross section of several spirals 4| on insulating sheets 42, the inneriori outer end of eachspiral being folded to abut: on the inner or outer end of its neighbour; thespirals are held together by the bolt 43which exerts-sufficient pressure to make a metallic connectionat the points of abutment. If an iron core is: to be used the centres of the spirals of Figure '7 are punched out along the dottedlines tgl before -fo1ding,'and the insulation between spiralsmay also be punched outas indicated by the dotted circlessurrounding thespirals.

Figure 9 may be referred to here as illustrating.

v In addition alternate pairs of lines 5| are joined further from the edge of the pattern so that if the extreme edges are sheared ofi the lines Will be electrically in series. Again it is to be noted that exigencies of drawing make Figure 9 highly diagrammatic; in fact the pattern can be of enormously greater length, and be composed of a very great number of closely spaced lines. Figure 9 will be further described below.- It is mentioned here as completing the illustration of the circuit component shown in Figure 10. In this Figures 55 and 56 show the two ends of a long strip of flexible insulation bearing a pattern of parallel metallic lines, such as is illustrated-in Figure 9, but in this case without any .end connections between the lines. This pattern is-here used as the basis for making a'helical winding to serve as an inductance, or as the winding of a transformer or for like purposes. After printing and development of the metallic lines the strip is wound upon a former or upon a core and closed. It would ordinarily be a very tediousop-y eration to wind a wire winding upon a closed-core, perhaps involving threading the bobbin through the core some thousands of times. But when it is remembered that the strip of Figures 9 and 10 may have hundreds of conductors side by side,.lt will be understood that thousands of turns of wire may be wound about a core by threading such a strip through it only a few times. However, the winding of the strip on the core in this manner only leaves the core winding with, say, a thousand separate conductors each encircling the core a few times. It remains to join these conductors in series. which involves, say, joining the end of the lowermost conductor in the end 55 of the strip to the uppermost in the end 56 and so on. This is conveniently done by the aid of a label 51 of transparent insulating material bearing a pattern of parallel conductors of similar spacing to the conductors of the strip'55, 5t insulated at their middle partsbut bare and solder-painted at their ends. In order thatthis label may be accurately applied to the ends 55.

56, as is necessary considering the close spacing of the conductors, the label is not only printed but embossed,,preferably in the printing operation, so that the ends of its conductors lie in grooves. Figure 11 shows a section of the label 51 and. of the end 56 upon the lines XII-XII of Figure 10, and shows the end of the label superposed. upon the end of the strip. It will be seen that the embossed parts of the label will fit between the conductors of the strip and thereby cause the conductors of strip and label to be accurately. superposed. A soldered joint is made by heat and pressure. The flaps 58 of the label maybe coated with adhesive and folded around and made adherent to the back of the ends. 55, 56. v

If it is desired to have parallel conductors upon a strip such as that of Figure 9, or the strip 55, 56 of Figure 10, more closely spaced than lines can reliablybe printed, the spacing of the lines may be increased to a little more than the width of the lines, and. after printing and metallising' the lines may be varnished with plastic. The strip can then be folded about a mid line (59, 59, Figure 10), running lengthwise of it, so that the conductors of one half of the strip come to lie between those of the other half; this is seen in Figure 12 which is a cross-section of such a folded strip, 61 being the insulating backing, 52 the conductors, and 63 their insulating coating.

Figures 7, l and 11 illustrate different ways in which the electro-conductive part of a circuit component originally printed on a flat sheet, or maybe on a cylinder, may be deformed into a three dimensional structure; Figures 13 and 14, showing an alternative way of building a cylindrical coil, for instance a relay winding, illustrate athird kind of deformation. In this case the printed pattern consists of a great number of elongated approximately rectangular turns one within the other; the middle part of the figure is broken away to indicate that its lengthmay be large compared with its width. When this is metallised the conductor is continuous from end j to end. It is formed into an inductive winding by stamping out its middle as indicated by the dotted line and winding it on the two-part core or former shown in Figure 14, preferably so that its ends become superposed, and then turning one part of the core or former end for end, thereby twisting the ends of the rectangular pattern, and bringing its long sides into juxtaposition with the current traveling around the core in the same direction in all of them.

The invention is by no means confined to. the:

building of circuit components for radio receivers. The pattern of parallel lines described with reference to Figure 9 is a typical pattern for the production of electrical resistances, for example for all kinds of heaters.

A resistant conductor such as indicated in Figure 9 may be formed upon wall-papers, wall and, furniture panels, curtains, and other hangings, and the like for the purpose of making electric heaters or rather warmers of them. Such a conductor, though of small thickness, will carry a substantial current because its flat form promotes loss of heat by radiation and conduction. The conductor will be insulated and protected by a covering, for instance of a varnish or plastic on which powdered metal oxide may be dusted to increase radiation; in the case of aluminium the conductor is preferably covered by oxidation for the same reasons.

When used on ordinarily ornamental fabrics such as wall-papers the pattern of Figure 9 may be made to provide or contribute to the ornamentation by a double printing process. There is first produced a pattern of parallel lines of say, aluminium, copper, zinc, iron or nickel. Upon this any ornamental design 53 is printed in an insulating ink. The sheet is then made the cathode in anelectrolytic bath by which copper is deposited on the metal lines except where covered by ink. The final product is, as before, a sheet with a pattern of parallel lines of which those parts within the design are of higher resistance than the remainder. over-printed sheet may be anodised to bring about reduction in the cross-section of the unprotected parts.

However, the second pattern may be superposed merely for its ,appearance without any thought of making the pattern rather than the non-patterned part of the source of heat, or vice versa. In this case it may be desired to render the pattern of parallel lines inconspicuous to Alternatively thethe eye, by suitable dyeing of the base, or of the oxide-coated or otherwise insulated conductor. For such over-printing a pattern of parallel lines of aluminium may be used with advantage, and the sheet subjected to an anodising process and dyeing process by which effects of some beauty may be produced. By the use of dyes which change colour at a temperature above atmospheric and below that which the conductor, or a part of it, reaches when carrying current, a visual indication may be, given when the heat is on. Such substances are well known in the art.

A class of printed patterns deserving mention is the patterns for winding the toothed cores of dynamo-electric machines. In one form shown in Figure 15 the pattern is mainly a star, in which each ray is a group of parallel conductors '1! representing the conductors of one slot; the inner and if desired the outer ends of the rays are prolonged at an angle to their length to form end connections preferably of the form of involutes of a circle; the insulating material between the groups of slot conductors is removed as indicated by the doubled lines, so that the slot conductors may be, folded through a right angle to enter the slots. Or the slot conductors may appear in the pattern as parallel groups of parallel lines 13 (as seen in Figure 16) upon an insulating sheet which is to be wrapped around the slotted core, openings being punched between the slot conductors, as indicated by the dotted rectangles, for the passage of the teeth. The end connections may be brought into their roper relative position by folding of the insulating sheet. For example the pattern may consist of two rows of groups of parallel lines I3, 14, those of one row being joined to those of the other by other parallel lines 15 at an inclination to the groups, while the outer ends '16 of the group are prolonged at the same inclination. By folding this pattern about a line '11 at right angles to and mid-way between the groups, the latter are superposed in the same slots or made to lie side by side in neighbouring slots, while the inclined lines 15 and (6 become end connections of V form. The rectangular openings punched in the insulating sheet between the groups, as indicated by dotted lines encircle the teeth when the winding is, placed on the core.

The invention is even more readily applicable to dynamo-electric machines employing an armature of disc form or consisting of a plurality of discs, as in some types of multipole alternator and inductor alternator. One such disc is shown in Figure 17. The conductor 8| has its radial turns spaced a pole pitch apart, or in the case of the inductor a tooth pitch apart. The ground upon which the print is made and the metal built up may be stamped out as indicated by the dotted line 82.

This application is a division of my application Serial No. 520,991, filed February 3, 1944, now Patent No. 2,441,960, granted May 25, 1948.

I claim:

1. A method of manufacturing a component of an electric circuit involving a conductive pattern of such weak mechanical structure that it is incapable of self-maintaining its configuration, said component including at least one conductor linking at least two terminals of said electric circuit of different operating potentials and including metallic joints for at least one other electric device not contained within said component, which comprises providing a sheet of metal foil with an impervious insulating backing, printing a representation on the surface of the metal foil of the conductive pattern of the component, including junction points which register with said metallic joints, in a medium adherent to said foil and protecting it from chemical at tack on the areas of said pattern, subjecting the metal foil to a chemical action utilizing the differentiation resulting from the imprint to produce a differentiation of conductive and nonconductive parts of the metal foil, and making electric connections at said junctions.

2. A method of manufacturing a component of an electric circuit according to claim 1 wherein the printed metal foil is subjected to the chemical attack of an etching fluid and the metal not covered by the protective medium is completely dissolved.

parts of the metal foil.

- 4. A method of manufacturing a component of an electric circuit according to claim 3 wherein the metal foil is made the anode in the electrolytic bath andv the metal on the unprotected areas of the foil dissolved.

' 5. A method of manufacturing a component of an electric circuit according to claim 3 wherein the metal foil is made the anode in an anodizing bath and the metal on the unprotected areas of the foil is anodized throughout its thickness.

6. A method of manufacturing a component of an electric'circuit according to claim 1' including the additional 'steps of deposition of metal upon at least selected parts of the metallic foil pattern of the component.

7. A method of'manufacturing' a component of an electric circuit involvinga conductive pattern of such .weak mechanical structure that it isiincapable of self-maintaining its configuration, said component including at least one conductor linking at least two terminals of said elec-' of metal foil with animpervious insulating backilk I2 i'rig" between'them, printing a representation on theexposed surface of one ofthe sheets ofmetal foil of a portion of the conductive patternof the component, including junction points Which-register with said metallic joints, in a medium adherent to said foil; printing a representationbf anotherportion' of said conductive pattern on the exposed surface of the other sheet of metal ing the additional step of increasingthe electrical resistance of selected portions of the metal" foil conductors of the pattern by exposing saidflportions'to chemical action ofa liquid thereby-re ducing the metallic "cross-section of said conductors.

' PAUL EISLER.

' REFERENCES CITED' The following references are of 'recordin the file of patent: I r UNITED STATES PATENTS Number Name Date 1,582,683 Harmon -Apr.' 2'7, 1926 1,623,666 'Ferkel Apr. 5, 1927 1,647,474 Seymour Nov. 111927 1,777,353 Davis Oct; 7;1'930 2,137,456 Palm Nov; 22; 1938 2,166,366 Norris "July '18, 1939 2,166,367 Norris July 18,1939 2,205,466 'Caprid-et a1. July'- 25; 1940' 2,261,473 Jennings 'N'ov:'= 4, 1941 2,288,735 "-OGonnell J uly""7;*1942 2,379,459 *Schriber July- 3, 1945 2432;800 Reiclidld "Ecol-1611947 2,441,960 Eisler l May 25, 1648 FOREIGN PATENTS Number Country 1 Date 670,106 Germany Jan? 11,1939 

